Jim Bonsey achieved his most significant innovation in the 1980s when he adjusted a car’s weight distribution to improve its handling. For balance, he moved the engine beside the cockpit and put the transmission on the other side. He called it the Sidewinder.

ST. PETERSBURG — If most people drove past J.B.'s Automotive on Central Avenue across from Haslam's Book Store without knowing about the shop or its owner, there's probably a good reason for that.

Most people don't drive cars made by Lamborghini, Ferrari or Rolls-Royce.

Nor do many people try their luck at amateur auto racing, a sport that poses physical and economic hardships without making anyone rich.

Yet between high-end car owners and racing aficionados, owner Jim Bonsey prospered. He designed and built open-wheel race cars of his own invention, 18 of which he sold.

At the time of his death last week, Mr. Bonsey was nearly finished with a new design — a poor man's race car he planned to build himself at a fraction of the cost.

Now that future is uncertain. Mr. Bonsey, a quiet man who thirsted for speed, died Nov. 16, six days after he collapsed inside a Walgreens store. He was 57. The cause of death is unknown.

He opened J.B. Automotive in 1979 and quickly established himself as the high-end mechanic of choice. Clients included well-known race car driver Augie Pabst; ex-jewel thief and security expert George Feder; and musician Roger McGuinn, who co-founded the Byrds.

But Mr. Bonsey didn't go into business to fix other people's cars. He wanted to build cars, then push them to run faster than anyone else's. If he wasn't driving at Florida tracks from Key West to Daytona Beach, he was running full speed up Chimney Rock Mountain in North Carolina, needing just two minutes to get from the bottom of the mountain to the summit.

Or racing at Mid-Ohio Sports Car Course, or Road America in Wisconsin.

After nearly every test run and nearly every race, he challenged his teammates with the same question: "Do we need to make it faster?"

He was willing to pay the price to do it. Mr. Bonsey had driven off the side of Chimney Rock and into trees. He had driven into mangroves even though he was profoundly allergic to mangroves.

"There was a pileup at Sebring," recalled longtime racing buddy Tom Stevens, 42. "He was underneath some cars at the start of the race. He walked away, no problems. But to watch it, it was like, 'Good Lord!' "

Though he saw his share of checkered flags, it was Mr. Bonsey's skills as a designer and machinist that truly set him apart.

He would redesign a clutch, shorten exhaust pipes or sculpt air tunnels in the body of a car to get an edge. He built an open-wheeled car with steering in all four wheels.

Mr. Bonsey achieved his most significant innovation in the mid 1980s when he adjusted a car's weight distribution to improve its handling. Until then, his colleagues said, race cars typically carried 55 percent of their weight in the back end, where the engine was.

To balance that, Mr. Bonsey moved the engine beside the cockpit, and put the transmission on the other side. He called his baby the Sidewinder.

The new model was a hit within the tightly knit racing community. Mr. Bonsey built and sold 18 Sidewinders.

James Joseph Bonsey was born in St. Petersburg, the son of former Pinellas County Commission Chairman John W. Bonsey. He built his first go-cart at age 12.

He attended Bishop Barry High School (now St. Petersburg Catholic), and met Debi Voissem at a school dance. They married in 1976.

In 1979, he sold his part of a Clearwater machine shop to start J.B. Automotive with his father. As his reputation grew, he began building car parts for customers around the world.

"He was the quintessential think-outside-the-box type of individual," said Mike Moench, 51, who joined Mr. Bonsey as service manager in the 1980s. "He would start with ideas that were way wild, out in left field. Then he would refine them down and bring them into reality."

In 1999, Mr. Bonsey sold the auto repair business to Moench, who opened J.B. Import Automotive Repair, three minutes away on 16th Street N.

Mr. Bonsey continued to design race cars at the old shop, and was nearly finished designing a car he planned to build from scratch. That model, a closed-wheel "Class D racer" under the Sports Car Club of America, would sell for a little more than $20,000.

For comparison, some racing enthusiasts now pay up to $100,000 for a comparable car built with European parts.

"He made this car so that the average person can get in there and be competitive," said Debi Bonsey, 56.

That model is just a suggestion now, its carbon fiber body weighing little more than cardboard.

"Everything you see around here is like an unrealized dream," said Gary Davis, a friend and longtime racing buddy. The challenge, he said, is how to finish the work of an inventor.

"Maybe Mike (Moench) can do something with it," said Davis, 63. "But ain't none of the other ones of us can, and none of his competitors could. We couldn't pick up where he left off. We couldn't even start where he started out."

One detail won't need second guessing — the name. Mr. Bonsey planned to call his everyman racer the Spirit.

Andrew Meacham can be reached at (727) 892-2248 or ameacham@sptimes.com.

.Biography

James Joseph Bonsey

Born: Nov. 6, 1953.

Died: Nov. 16, 2010.

Survivors: Wife Debi; parents John and Jean Bonsey; daughters Victoria Jiencke and her husband Steve, Amy Freda and her husband A.J., and Leah Bonsey; and one granddaughter.